Cooling system for xenon arc lamps

ABSTRACT

A cooling system for lamps, such as Xenon arc lamps used in motion picture projectors, where the lamp is elongate with a terminal and seal at each end, with one terminal and seal mounted within the mirror and thereby subjected to excessive heating. A concentric sleeve construction for the seal within the mirror and an air supply duct providing cooling air flow diectly about the seal and protecting the seal from reflected radiation.

United States Patent 1 1 [111 3,843,879 Eddy 1451 Oct. 22, 1974 [54]COOLING SYSTEM FOR XENON ARC 3,559,816 2/1971 Hirata 240/47 x L S3,626,176 12/1971 Tsugami... 353/61 X 3,700,881 10/1972 Slomskim.240/4135 R n o Richard dy, C sta Mesa. Calif. 3,703,635 11/1972 Burkarth240/4135 R 73 Assi nee: Christie Electric Cor Los 1 g Angeles Ca pPrimary Examiner-Rwhard M. Sheer Attorney, Agent, or Firm-Harris, Kern,Wallen & [22] F1led: Feb. 12, 1973 Tinsley [21] Appl. No.: 332,020

[57] ABSTRACT [52] U S Cl 240/47 352/202 353/61 A cooling system forlamps, such as Xenon arc lamps [51] Fzlv 29/00 used in motion pictureprojectors, where the lamp is [58] Fieid 353/52 elongate with a terminaland seal at each end, with 353/57 one terminal and seal mounted withinthe mirror and thereby subjected to excessive heating. A concentric [56]References Cited sleeve construction for the seal within the mirror andan air supply duct providing cooling air flow diectly UNITED STATESPATENTS about the seal and protecting the sea] from reflected 3,188,4596/1965 Bridwell 240/47 radiation 3,305,680 2/1967 Berkl 240/47 3.465.1409/1969 061661111111 240/47 x 3 Cla ms, 4 Drawmg Figures 1, COOLINGSYSTEM FQR XENON ABC LAMPS being used in place of the earlier carbon arclights toprovide a light source for motion picture projectors. The Xenonlamps provide a superior light output, but considerable problems havebeen encountered in the installations due to premature failure of thelamps.

A typical Xenon arc lamp comprises a generally tubular glass housingwith an electrode projecting from eachend and defining the arc spacebetween the electrodes at the center of the housing. A glass-to-metalseal is provided at each end of the lamp between the housing andrespective electrode, with the end of the electrode projecting from theseal to serve as a terminal for electrical connection.

It has been determined that the majority of the premature failures ofthe Xenon lamps results from excessive heating of the area around theseal. Attempts have been made to reduce the heating by directing a jetof air onto the seal area of the lamp, but this approach has not beensatisfactory, particularly with regard to the seal positioned within theelliptical mirror. Although a part of the heat generated by the lamp isconducted through the electrode and the glass envelope to the I seal, Ihave found that a very substantial amount of heat is reflected byradiation from the mirror to the seal area. By providing a brightreflecting shield around the seal area, in addition to a cooling airstream properly conducted within the shield, it is possible to greatlylower the seal temperature.

Accordingly it is the object of the invention to provide a new andimproved cooling system particularly adapted for use with the end of aXenon arc lamp positioned within the mirror of a motion pictureprojector lamp housing or the like. A further object is to provide sucha cooling system incorporating a unique sleeve construction about theseal with an air supply for directing air in a predetermined path aroundthis seal. An additional object is to provide such a cooling systemincluding a highly reflecting sleeve about the seal protecting the sealfrom radiation from the reflecting mirror. Other objects, advantages,features and results will more fully appear in the course of thefollowing description.

In the drawing:

FIG. 1 is an isometric view of a light source for a motion pictureprojector or the like, incorporating a presently preferred embodiment ofthe invention;

FIG. 2 is an enlarged sectional view of the lamp installation of thesource of FIG. 1; I

FIG. 3 is an enlarged sectional view taken along the line 3-3 of FIG.'2;and

FIG. 4 is a sectional view taken along the line 44 of FIG. 3.

In FIG. 1, the cooling system of the invention is incorporated in anotherwise conventional light source. An elliptical mirror is supportedon a mirror frame 11 within a cabinet 12. A Xenon arc lamp 13 ispositioned within the mirror 10, as shown in detail in FIG. 2, with thelamp output being directed by the mirror 10 through a lens 15. A powersupply for the lamp, appropriate controls, and a blower to supplycooling air may be incorporated in the cabinet 12, with a duct 16serving as an exhaust duct. The levers 17' are conventional dowserhandles for shutting off the light output, and plate 18 is a cover forthe conventional lens cleaning access opening.

The lamp 13 may be a conventional Xenon arc lamp and is shown in greaterdetail in FIG. 2, including a housing 21 and electrodes 22, 23. Theelectrode 22 is joined to the housing 21 at a glass-to-metal seal 24,with the electrode projecting from the housing to provide an electricalterminal at 25. Similarly the electrode 23 is joined to the housing 21in a glass-to-metal seal 26, with the electrode projecting to provideanother terminal 27.

The lamp may be supported by the terminal pin 25 carried in a bracket 34and secured by a nut 35. The bracket 34 is fastened to a plate 33carried by a support bracket 37. An electrical connection may be made toterminal 25 by the conducting bracket 34 and the nut 35. A power supplymay be connected to the bracket 34 at a terminal 36.

A sleeve 38 may be carried on the plate 33 about the lamp, and be heldin place by springs 39 positioned between pins carried on the plate 33.

A tube 31 is carried between the sleeve 38 and the mirror 10 and anothertube 32 is carried on the tube 31 and the plate 33. Cooling air issupplied to the left end of the sleeve 38 from a blower (not shown) forflow through the tube 31 about the seal 24 and also for flow throughopenings 40 in the sleeve 38 into the annular passage between the tubes31, 32. Thetubes 31 and 32 are of sufiicient diameter to eliminatedirect radiation to the seal 24.

The cooling system of the invention is installed about the seal 26 andis shown in greater detail in FIG. 4. A duct is supported at its lowerend in a block 51 typically mounted in a bracket 52. Air is supplied tothe duct 50 from a blower (not shown) through a line 53 and the block51.

A sleeve 54 is carried at the upper end of the duct 50, with an opening55 in the side of the sleeve providing for air flow from the duct to thesleeve. Another sleeve 56 is carried within the sleeve 54 by means of anend plate 57 and an intermediate plate 58. The duct, the sleeves and theplates may be fastened together to form a unitary structure, typicallyby welding. Openings 60 are provided in the sleeve 56, with the openings60 disposed around the sleeve.

The lamp 13 is positioned with the seal 26 within the sleeve 56 and withthe terminal 27 projecting through the end plate 57 for connection to anelectrical fitting 62.

In the preferred embodiment illustrated in the drawing, the inner sleeve56 projects over the glass-to-metal seal of the lamp, while the outersleeve 54 projects beyond the inner sleeve toward the arc zone of thelamp. In operation, the electrical supply is connected to terminal 36and fitting 62 to produce an are between the electrodes in the lamp. Themajor portion of the radiation from the arc is directed to the right bythe mirror 10, but a portion of the radiation is directed toward theseal area of the lamp. The sleeves function to protect the seal fromthis radiant heating, and the performance of the sleeves is enhanced byproviding a bright reflecting finish on the outer surface of the outersleeve 54. Air under pressure is directed through the duct 50 into thezone between the outer and inner sleeves 54, 56 and the plates 57, 58.This zone serves as a manifold for feeding air through the opening 60 sothat the cooling 3 air directly contacts all sides of the glassto-metalseal, with the air exhausting along the annular passage beinto the outersleeve and exits generally radially through slot 64 in the outer sleeve54. The air flow paths are indicated by the arrows on FIG. 4.

With the unique cooling system of the invention, the lamp seal ismaintained at a temperature sufficiently low as to not adversely affectthe glass-to-metal seal so that the operating life of a lamp is notreduced by seal failure.

I claim:

1. In a lamp cooling system, the combination of:

a cabinet;

a generally ellipsoidal mirror having an axis and mounted within saidcabinet;

an elongate lamp having a lamp housing with first and second seals, saidlamp having first and second inline terminals entering the lamp housingat the first and second seals, respectively, with the lamp positionedwithin said mirror along said axis with said first seal and terminal infront of said mirror;

a sleeve positioned about said lamp at said first seal substantiallyconcentric with said axis and defining an annular air flow passagebetween said seal and tween the lamp and the inner sleeve. The air thenflows sleeve, with said sleeve substantially closed at one end;

a radially positioned supply duct coupled to said sleeve between saidfirst seal and one end;

means for supplying air under pressure to said supply duct for flow intosaid sleeve and through said annular passage about said first seal;

a second sleeve positioned about said one sleeve and extending alongsaid lamp beyond said first seal and terminating short of the source oflight within said lamp housing; and

baffie means'engaging said sleeves defining a manifold therebetween;

said supply duct being connected to said second sleeve at said manifold,and said one sleeve having passage means for air flow from said manifoldinto said one sleeve. I 2. A system as defined in claim 1 wherein saidpassage means comprises a plurality of openings spaced around said onesleeve.

3. A system as defined in claim 1 wherein said second sleeve includes anexhaust opening in the side thereof for air flow from said annularpassage in a generally radial direction away from said lamp.

1. In a lamp cooling system, the combination of: a cabinet; a generallyellipsoidal mirror having an axis and mounted within said cabinet; anelongate lamp having a lamp housing with first and second seals, saidlamp having first and second in-line terminals entering the lamp housingat the first and second seals, respectively, with the lamp positionedwithin said mirror along said axis with said first seal and terminal infront of said mirror; a sleeve positioned about said lamp at said firstseal substantially concentric with said axis and defining an annular airflow passage between said seal and sleeve, with said sleevesubstantially closed at one end; a radially positioned supply ductcoupled to said sleeve between said first seal and one end; means forsupplying air under pressure to said supply duct for flow into saidsleeve and through said annular passage about said first seal; a secondsleeve positioned about said one sleeve and extending along said lampbeyond said first seal and terminating short of the source of lightwithin said lamp housing; and baffle means engaging said sleevesdefining a manifold therebetween; said supply duct being connected tosaid second sleeve at said manifold, and said one sleeve having passagemeans for air flow from said manifold into said one sleeve.
 2. A systemas defined in claim 1 wherein said passage means comprises a pluralityof openings spaced around said one sleeve.
 3. A system as defined inclaim 1 wherein said second sleeve includes an exhaust opening in theside thereof for air flow from said annular passage in a generallyradial direction away from said lamp.